434 THE CRYSTAL FALLS lEOiv^-BEARING DISTRICT. 



dolomite strikes and dips toward all points of the compass. This irreg'ularity 

 is caused by the gentle arching over the general nortliAvest-southeast axis, 

 combined with much sharper local folding about a series of axes which run 

 more nearly east and west. The best-defined east-and-west folds occur 

 west of the main axis in sec. 32, T. 44 IST., R. 31 W., in Avhicli three syn- 

 clines and three anticlines are found along a north-and-south section 4,000 

 feet long'. The two southern synclines are sufficiently deep to include the 

 overlying Mansfield phyllites. The secondary folds die out toward the 

 main north-and-south axis and broaden toward the west. East of the 

 main axis but one secondary fold has been recognized, namely, the syncline 

 which forms Michig'amme Mountain. This is the deepest of the secondary 

 folds, and the only one containing the Grroveland formation. 



PETROGRAPHICAL CHARACTERS. 



The Randville formation in this area is richer in lithological varieties 

 than in the Felch Mountain range. As originally deposited, a much larger 

 proportion of sand and mud was mingled with the carbonates, and the prog- 

 ress of subsequent metamorphism also has been less uniform. Depending 

 upon the interaction of these two factors, we find, as the extremes of variation, 

 on the one hand coarse saccharoidal marbles, sometimes very pure, but 

 most often filled with secondary silicates, and on the other hand fine-gi'ained 

 little-altered limestones, which occasionally are so impure as to be rather 

 calcareous or dolomitic sandstones and shales. The more impure varieties 

 occur, as might be expected, near the contacts with the adjacent formations. 



On the Fence River, in sec. 16, T. 44 N., R. 31 W., the base of the 

 dolomite rests on the Sturgeon formation. The rock is filled with grains of 

 quartz and feldspar and scales of chlorite, and is so soft that it may be 

 crushed between the fingers. In sec. 32, T. 44 N., R. 31 W., the top of the 

 formation is in contact with the Mansfield slates, and between them is a com- 

 plete series of transition beds. Near the junction the limestone becomes dark 

 colored and contains thin bands in which the clayey material greatly exceeds 

 the carbonates. These are succeeded by alternating beds of slate and impure 

 limestone in nearly equal volume, and it is only high up in the slate member 

 that the calcareous bands completely disappear. Apart from these belts of 

 extreme impurity at the base and to^i of the formation, the presence of scat- 

 tered fragmental grains of quartz and feldspar is rather general tlu-oughout. 



The prevalent colors are white, various shades of pink, both light and 



